undefined reference in linking against C++ library

Question

I write a C++ library and when linking against the library the symbols in it cannot be found. Here's what I've got:

a.cpp:

void zak()
{
}

test.cpp:

extern void zak();

int main(int argc, const char ** argv)
{
    zak();
}

Makefile:

all:
    g++ -c -o a.o a.cpp
    ar r libzak.a a.o
    g++ -L. -lzak test.cpp -o test

Here is what make says on my (Linux Mint 13) box:

g++ -c -o a.o a.cpp
ar r libzak.a a.o
g++ -L. -lzak test.cpp -o test
/tmp/ccC4cnLV.o: In function `main':
test.cpp:(.text+0x7): undefined reference to `zak()'
collect2: error: ld returned 1 exit status
make: *** [all] Error 1

I am sure I am missing something obvious, but what is it?

We can kinda work it out from the title of the question, but could you please edit the question itself with the precise error messages? — NPE, Feb 06 '14 at 16:24

score 5 · Accepted Answer · edited May 23 '17 at 10:31

5

Link order matters. Put -lzak after test.cpp on the link line.

edited May 23 '17 at 10:31

Community

1
1

answered Feb 06 '14 at 16:12

NPE

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score 0 · Answer 2 · answered Feb 06 '14 at 16:29

0

I think that -l is for shared libraries (.so). Try this: g++ libzak.a test.cpp -o test

answered Feb 06 '14 at 16:29

gabriel

235
1
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`-l` is for both static and shared libraries. – NPE Feb 06 '14 at 17:56

undefined reference in linking against C++ library

2 Answers2